As promised, I sent James E. Swain some questions about his study comparing the MRI scans of mothers who delivered vaginally to mothers who delivered by c-section. The results of the study seemed to show that only the mothers who delivered vaginally had bonding signals light up when hearing a recording of their baby cry.

Dr. Swain’s unedited answers to my questions are below:

Was it documented which mothers breast fed, and did such a factor make a difference in the statistics?

For this study, we chose mothers who all were breastfeeding. However, we have looked at breast- vs. formula-feeding mothers as a way to get at altered oxytocin levels and there are differences in brain responses to baby stimuli. We have a manuscript in preparation.

Did any of the mother’s have postpartum depression? How did that effect the data?

The mothers in our study were all well with no personal or family history of mental health diagnoses and none of them developed postpartum depression. We are beginning to study mothers at risk for postpartum depression or actually suffering peripartum mental health problems toward developing tests for early detection and optimal treatment of peripartum health problems.

Did all the mothers who delivered a vaginal birth use an epidural? Did any of them go through labor and delivery without drugs?

For this first study we took all subjects, so some of our subjects took pain medications and others did not. We hope to control this variable in future studies.

What specific areas of the brain were being looked at in the MRI scans?

We looked at the entire brain. Specific areas of relatively higher responsiveness to baby cry in vaginal compared to cesarean delivering mothers are listed in the paper and broadly described in the press release.

How can any we attach any significance to data from such a small sample size? Why did you choose to make it so small? Will you be planning on expanding the study?

The number of subjects was not by choice. Of course we would rather have larger sample sizes, but this is limited by time and money. When the request for papers in this area from the journal was posted, we responded with the numbers that we had. However, the number did satisfy statistical testing and many studies in cognitive neuroscience with brain imaging are currently being published with simlar numbers. This is partly possible because we measure brain activity in each subject many times (rather than just asking a question for example). We are working on larger sample sizes, and populations at risk for depression. These experiments are expensive and it is challenging to recruit subjects willing to participate in the early postpartum. Hopefully the attention that this paper is receiving will help us raise funds to replicate our results with better controls and hopefully develop intervention trials to improve the postpartum for all.

Do you think that women who show bonding signals in their brain have an advantage over those who don’t?

It’s hard to say at this point. It may be that our statistically significant results are not clinically significant – especially for healthy mothers. I suspect that some mothers are at risk for peripartum mental health problems and that brain imaging may be able to detect such risks and that some interventions – perhaps some straightforward support and cognitive psychotherapy may be abe to head off many problems

How do you explain the disparity between the self-reported feelings of the c-section mothers and the lack of corresponding areas of brain stimulation?

The brain has many different areas and I would not expect all areas of response to vary with delivery mode. For instance, brain areas related to attention may not be affected.

Reports of this study often bring up oxytocin as a possible bonding chemical missing in the c-section group of mothers. Do you have any other alternate theories that don’t involve oxytocin?

The difference in mode of delivery are multifaceted from family, culture, personal factors as well as the biological mechanisms that may involve oxytocin. All are worthy of study and may be means of understanding as well as targets of therapy.

Thanks to Dr. Swain for taking the time out of his busy schedule to discuss this issue. Best of luck to him on continuing this area of research! Attached below is the press release that he added to the bottom of his message. I reprint it here to clear up any confusion that any readers may have about the way the mainstream media and I have interpreted the study.

Natural Childbirth Makes Mothers More Responsive to Own Baby-Cry

Research news from The Journal of Child Psychology and Psychiatry

A new study has found that mothers who delivered vaginally compared to caesarean section delivery (CSD) were significantly more responsive to the cry of their own baby, identified through MRI brain scans two to four weeks after delivery.

The results of the study, to be published today in The Journal of Child Psychology and Psychiatry, suggest that vaginal delivery (VD) mothers are more sensitive to own baby-cry in the regions of the brain that are believed to regulate emotions, motivation and habitual behaviours.

CSD is a surgical procedure, in which delivery occurs via incisions in the abdominal and uterine wall. It is considered necessary under some conditions to protect the health or survival of infant or mother, but it is controversially linked with postpartum depression. In the US the occurrence of CSD has increased steeply from 4.5% of all deliveries in 1965 to a recent high in 2006 of 29.1%.

The critical capacity of adults to develop the thoughts and behaviours needed for parents to care successfully for their newborn infants is supported by specific brain circuits and a range of hormones. The experience of childbirth by VD compared with CSD uniquely involves the pulsatile release of oxytocin from the posterior pituitary, uterine contractions and vagino-cervical stimulation. Oxytocin is a key mediator of maternal behaviour in animals.

“We wondered which brain areas would be less active in parents who delivered by caesarean section, given that this mode of delivery has been associated with decreased maternal behaviours in animal models, and a trend for increased postpartum depression in humans,” said lead author Dr. James Swain, Child Study Centre, Yale University. “Our results support the theory that variations in delivery conditions such as with caesarean section, which alters the neurohormonal experiences of childbirth, might decrease the responsiveness of the human maternal brain in the early postpartum.”

The researchers also looked into the brain areas affected by delivery conditions and found relationships between brain activity and measures of mood suggesting that some of the same brain regions may help regulate postpartum mood.

“As more women opt to wait until they are older to have children, and by association be more likely to have a caesarean section delivery, these results are important because they could provide better understanding of the basic neurophysiology and psychology of parent-infant attachment,” said Swain. “This work could lead to early detection of families at risk for postpartum depression and attachment problems and form a model for testing interventions.”

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This study is published in the October 2008 issue of The Journal of Child Psychology and Psychiatry. Media wishing to receive a PDF of this article may contact wbnewseurope@wiley.com

About the author: Dr. James Swain MD, PhD is based at the Child Study Centre at Yale University. Dr. Swain has been working in this field for 5 years and is among the first to do brain imaging of parents using baby-stimuli. His background includes a basic neuroscience PhD, MD training and subsequent psychiatry and child psychiatry specialty training before beginning this work. To arrange an interview, please contact the Office of Public Affairs at Yale University on 001-203-432-1345 / oropa[at]yale.ac.edu or contact Dr. Swain directly on 001-203-785-6973 / james.swain[at]yale.edu.

About the journal:The Journal of Child Psychology and Psychiatry, published by Wiley-Blackwell on behalf of the Association for Child and Adolescent Mental Health, is internationally recognised to be the leading journal covering both child and adolescent psychology and psychiatry. Articles published include experimental and developmental studies, especially those relating to developmental psychopathology and the developmental disorders. An important function of the Journal is to bring together empirical research, clinical studies and reviews of high quality arising from different points of view. The Journal of Child Psychology and Psychiatry can be accessed online at: www.blackwellpublishing.com/jcpp

About The Association for Child and Adolescent Mental Health: The Association is a learned Society managed by an elected Council within a Constitution accepted by the membership. The Objects of the Association are the scientific study of all matters concerning the mental health and development of children through the medium of meetings and the establishment of The Journal of Child Psychology and Psychiatry, Child and Adolescent Mental Health, and the ACAMH Occasional Papers series, in which scientific matters can be discussed, and clinical findings, research projects and results can be published. The Association is multi-disciplinary in nature, and exists to further child psychology and psychiatry. Membership of the Association does not confer professional status on any individual.For further information, please visit www.acamh.org.uk/